1. Field of the Invention
The present invention relates to a method of processing filament yarns for rubber hoses made of polyamide to be coiled and buried in the rubber hoses to be treated with vulcanization.
2. Description of the Related Art
Conventionally known rubber hoses are reinforced with fibers (filament yarns) coiled around an inner tube with predetermined spaces. Namely, as shown in Fig.7, such a rubber hose 51 is in general produced by extrusion-molding an inner tube rubber 52, coiling filament yarns 53 therearound, extruding and supplying a cover rubber 54 therearound, and performing the vulcanization thereon. However, as shown in the same, the rubber hose 51 produced as mentioned above is that the filament earn 53 causes shrinkage due to the heat at the time of vulcanization, and bite into the inner tube rubber 52, whereby the inner tube rubber 52 reduces its thickness, otherwise the inner tube rubber 52 and the cover rubber 54 are probably caused with unevenness in the inner and outer surfaces thereof.
As a technology for solving such inconveniences, there is known an art disclosed in Japanese Patent Publication No. Sho. 63-63798. For producing rubber hoses, this art at first carries out the dry-heating treatment at an ordinary humidity under a condition of applying tension, and further prepares nylon filament yarns having been subjected to a wet-heating treatment under steam atmosphere under a condition of applying no tension thereto. The art then coils in spiral the thus treated nylon filament yarns on the outer circumference of the inner tube rubber, leaving spaces between the yarns, covers a cover rubber cover the outer circumference, and performs the vulcanization. Thus, by drying the nylon filament yarns under the condition of applying the tension thereto, and thereafter wet-heating it under the condition of applying no tension thereto, it is possible to provide such nylon filament yarns without largely lowering elastic coefficient and causing any shrinkage in relation with the heat at the vulcanization.
The nylon filament yarn coiled and buried in the rubber hose should firmly adheres to the rubber after the vulcanization. But said publication does not so much refer to a treatment for securing an adhesive property.
It is, thereupon, considered to coat a solution of an adhesive agent to the inner tube rubber at a step after the wet-heating treatment of the nylon filament yarn and before coiling it over the inner tube rubber, and operate the coiling after the drying step. Herein, as the solution of the adhesive agent, a RFL (resorcinol, formalin and rubber latex) solution is in general used. Due to the existence of RFL, the mutual adhesion between the nylon filament yarn and the rubber may be attained.
However, if the adhesion manner as above said is employed, a drying step after coating must be independently provided, resulting to invite increment of the number of treating steps and cost. Ii addition, if performing concurrently and continuously the extrusion of the inner tube rubber, the coiling of the nylon filament yarns and the extrusion of the cover rubber, the adhesive agent as said above is difficult to coat, subsequently to invite lowering of workability.